1 + 1 = 2

This equation reflects fundamental arithmetic known to everybody. The component numbers are numeric, measurable, logical, accurate (usually) and reproducible.  For the lay person its the numbers we come across in day to day living, when dealing with addition, subtraction division and multiplication.  The most common human example is the in the purchase of goods or food, where a particular product has a a price, and the transaction requires an exact amount of money in exchange

There are many instrument that require the arithmetic accuracy of numbers including thermometers, calculators, pressure gauges, PH meters, and scales for example. In biology and medicine it may be the mere counting of the heart rate, the number of white or red cells in the urine, the concentration of the blood sugar, or serum potassium.